Wrought 2xxx aluminum alloy product having an improved compromise between static properties and toughness, and method for manufacturing same

Abstract

A rolled 2xxx-series aluminum alloy product having a thickness of at least 50 mm, comprising in wt. %, Cu 4.5-4.9; Mg 0.5-0.6; Mn 0.2-0.4; Zn 0-0.1; Ti 0.02-0.07; Ag 0.1-0.4; Zr 0.08-0.15; Si 0-0.15; Fe 0-0.15; unavoidable impurities ≤ 0.05 each and ≤ 0.15 in total, the remainder being aluminum, such that, at mid-thickness, the grain structure of said product comprises, at mid-thickness, a surface fraction of recrystallized grains of 50% to 80%. Said rolled product being obtained by a manufacturing process comprising a controlled hot rolling step so as to have a hot rolling exit temperature of 410°C to 445°C.

Description

[0001]DESCRIPTION Title: Wrought product of 2XXX aluminum alloy having an improved static-toughness compromise and its manufacturing method. Technical field The present invention relates to a wrought product of 2XXX aluminum alloy having a thickness greater than or equal to 50 mm, preferably from 90 mm to 160 mm, having improved properties with regard to the static-toughness compromise and a manufacturing method intended to improve the static-toughness compromise while maintaining excellent resistance to stress corrosion cracking. Prior art Aeronautical applications generally require a very specific set of properties. In wing structure applications, the spar is generally made of 7xxx alloy because a good static-toughness compromise is sought for sheets with thicknesses greater than or equal to 50 mm, preferably from 90 mm to 160 mm.However, there is a demand for products with low sensitivity to crack deflection, which can achieve good fatigue cracking behavior. Among aluminum alloys, 2XXX alloys perform well in fatigue cracking. EP1641952 discloses an alloy having improved strength and ductility, comprising Cu3.5 - 5.8 wt%, Mg 0.1 - 1.8 wt% Mn 0.1 - 0.8 wt% Ag 0.2 - 0.8 wt% Ti0.02 - 0.12 wt% and optionally one or more elements selected from the group consisting of Cr 0.1 - 0.8 wt%, Hf 0.1 - 1.0 wt%, Sc 0.03 - 0.6 wt%, and V 0.05 -0.15 wt%, remainder aluminum and other incidental elements and impurities, and wherein the alloy is essentially free of zirconium.US 5,376,192 discloses a wrought aluminum alloy comprising about 2.5-5.5 wt% copper, about 0.10-2.3 wt% magnesium, about 0.1-1 wt% silver, up to 0.05 wt% titanium, and the balance aluminum, wherein the amount of copper and magnesium is kept below the solid solubility limit of copper and magnesium in aluminum. US Patents US 5,630,889, US 5,665,306, US 5,800,927 and US 5,879,475 disclose substantially vanadium-free aluminum-based alloys comprising about 4.85-5.3 wt% copper, about 0.5-1 wt% magnesium, about 0.4-0.8 wt% manganese, about 0.2-0.8 wt% of silver, up to about 0.25% by weight of zirconium, up to about 0.1% by weight of silicon, and up to 0.1% by weight of iron, the remainder being aluminum, incidental elements and impurities.WO2006 / 019946 discloses a 2000 series aluminum alloy, the alloy consisting essentially of about 3.0-4.0 wt% copper, about 0.4-1.1 wt% magnesium, up to about 0.8 wt% silver, up to about 1.0 wt% Zn, up to about 0.25 wt% Zr; up to about 0.9 wt% Mn; up to about 0.5 wt% Fe; and up to about 0.5 wt.% Si, the remainder being primarily aluminum, impurities and accessory elements, with copper and magnesium present in a ratio of about 3.6 to 5 parts copper to about 1 part magnesium.The alloy can be used in wrought or cast products, including those used in aerospace applications, particularly structural members in the form of thin sheet or heavy plate, extrusions and forgings, and provides an improved combination of strength and damage tolerance.WO2020 / 123096 discloses 2xxxx aluminum alloys that comprise 0.08 to 0.20 wt% Ti. The novel 2xxx aluminum alloys according to WO2020 / 123096 may exhibit an improvement in at least two properties from, for example, strength, fracture toughness, elongation, and corrosion resistance. WO2022 / 129806 discloses a method for thermomechanical treatment of wrought products made of a 2000 series aluminum alloy comprising, in wt%, Cu 3.5 - 5.8; Mg 0.2 - 1.5; Mn≤ 0.9; Fe ≤ 0.15; Si ≤ 0.15; Zr ≤ 0.25; Ag ≤ 0.8; Zn ≤ 0.8; Ti 0.02 - 0.15; unavoidable impurities ≤0.05 each and ≤0.15 in total; remainder of aluminum, allowing an improvement in resistance to stress corrosion. It includes a tempering composed of two sequences.The first sequence is defined by a maximum temperature T1max of 130°C to 180°C and by a holding time at a temperature between 130°C and 180°C which is equivalent to an equivalent time calculated at 160°C of between 10 h and 80 h. The second sequence is defined by a temperature T2°c (t) lower than T1max and a holding time t2 at a temperature between 100°C and 130°C, which is equivalent to an equivalent time calculated at 160°C such that it is between 0.3% and 15% of the equivalent time calculated for the first sequence. WO2023 / 028070 discloses a method comprising artificial aging of a 2xxx aluminum alloy in at least two steps.In one embodiment, the first aging step comprises aging a 2xxx aluminum alloy at a first temperature of between 300ºF (150°C) and 450ºF (230°C) and for a first aging time of between 4 and 120 hours, and aging the 2xxx aluminum alloy at a second temperature for a second aging time of between 30 minutes and 120 hours, wherein the second temperature is 20°F to 150°F lower than the first temperature. The novel two-stage artificial aging step may facilitate an improved combination of properties, such as an improved combination of two or more of strength, ductility, fracture toughness, and corrosion resistance.There is a need for thick products with a thickness greater than or equal to 50 mm, preferably between 90 mm and 160 mm, made of 2XXX alloy, having at mid-thickness both a tensile yield strength Rp0.2(L) and a compressive yield strength Rpc0.2(L) in the high L direction, a high toughness K1c(LT) in the LT direction, as well as a low tendency to crack bifurcation and good corrosion resistance.Disclosure of the invention The invention relates to a method for manufacturing wrought products made of 2xxx series aluminum alloy comprising the following steps:(a) casting an aluminum alloy plate comprising in wt%,Cu 4.5 - 4.9Mg 0.5 - 0.6Mn 0.2 - 0.4Zn 0 - 0.1Ti 0.02 - 0.07Ag 0.1 - 0.4Zr 0.08 - 0.15, preferably 0.10 - 0.13 or 0.10 - 0.12Si 0 - 0.15Fe 0 - 0.15Unavoidable impurities ≤0.05 each and ≤0.15 in total, remainder aluminum,(b) homogenizing said plate at a temperature of 480°C to 540°C for 4 to 80 hours,preferably from 10h to 60h,(c) optionally, said homogenized plate is reheated. Preferably, reheating during step (c) is carried out at a temperature of 410°C to 480°C,(d) said homogenized plate is hot-deformed by rolling to obtain an intermediate product having a thickness greater than or equal to 50 mm, preferably from 90 mm to 160 mm.In step (d) the hot rolling outlet temperature is 410°C to 445°C, preferably 420°C to 440°C, (e) said intermediate product is dissolved, (f) said intermediate product dissolved is quenched with water, (g) said intermediate product dissolved and quenched is pulled in a controlled manner with a permanent deformation of 3 to 6%, (h) said intermediate product thus dissolved, quenched and pulled is tempered by heating from 100 to 180°C for 5 to 100 hours. Preferably the total equivalent time t. tot eq at 160°C of the income achieved is 10 to 90 hours, preferably 13 to 40 hours. The total equivalent time ttot eq at 160°C is defined by the formule : where ^°^(^) corresponds to the change in temperature expressed in °C as a function of time t during tempering. In a preferred embodiment, during step (h) tempering is carried out in two stages, a first stage at a temperature of 140°C to 180°C for a duration of 10h to 100h, preferably 10h to 40h and a second stage at a temperature of 100°C to 130°C for a duration of 10h to 50h, preferably 15h to 30h. Preferably, the first stage is carried out at a temperature of 160°C + / - 5°C for a duration of 18h + / - 5h and the second stage at a temperature of 120°C + / - 5°C for a duration of 20h + / - 10h, preferably 20h + / - 2h. In a preferred embodiment, during step (d) the hot rolling inlet temperature is from 380°C to 460°C. The invention also relates to a rolled product made of 2xxx series aluminum alloy having a thickness of at least 50 mm, preferably from 90 mm to 160 mm, comprising in % in poids :Cu 4.5 - 4.9Mg 0.5 - 0.6, preferably 0.50 to 0.60Mn 0.2 - 0.4Zn 0 - 0.1, preferably 0 - 0.05Ti 0.02 - 0.07Ag 0.1 - 0.4Zr 0.08 - 0.15, preferably 0.10 - 0.13 or 0.10 - 0.12Si 0 - 0.15Fe 0 - 0.15Unavoidable impurities ≤0.05 each and ≤0.15 in total, remainder aluminum, and such that at mid-thickness, the grain structure of said product comprises a surface fraction of recrystallized grains of 50% to 80%, preferably 50% to 75%, the surface fraction of recrystallized grains is measured by EBSD and where a grain is considered recrystallized if it has a misorientation of at least 7° with the neighboring grain and the orientation of said grain has an extent of less than 2.5°, also called Grain Orientation spread (GOS).According to a preferred embodiment, the rolled product has a texture such that the volume fraction of the Copper component {112} <111> is greater than 4%, preferably 5% and / or the volume fraction of brass component {110} <112> is greater than 7%, preferably 8% and / or the volume fraction of component S {123} <634> is greater than 9%, preferably 11%. Preferably, the sum of the volume fractions at mid-thickness of the components of texturecopper {112} <111> , brass {110} <112> and S {123} <634> is greater than 20%. According to a preferred embodiment, the rolled product has, at mid-thickness, a tensile yield strength in the L direction, Rp0.2 (L) and a compressive yield strength in the L direction, Rpc 0.2 (L) each of at least 435 MPa. Preferably, the rolled product has, at mid-thickness, a toughness K1c (LT) measured according to ASTM E399 greater than or equal to 40 MPa.√m.The invention also relates to a structural element manufactured from a product according to the invention and / or obtained according to the method of the invention. Said structural element is intended for aerospace applications. Preferably, the structural element may be a spar in an aircraft wing, preferably an integral spar. The invention also relates to an armor element manufactured from a product according to the invention and / or obtained according to the method of the invention. Said armor element may be an armor plate, preferably an integral armor plate, intended for example for an armored vehicle. FiguresFigure 1 represents the compromise Rp0.2 (L)-K1c (LT) at mid-thickness of the different sheets tested in example 1. Figure 2 represents the evolution of the stress in the L direction according to the position in the thickness of the sheet.Figure 3 represents the evolution of the stress corrosion life as a function of the applied stress for a product according to the invention. Detailed description of the invention Unless otherwise stated, all indications concerning the chemical composition of the alloys are expressed as a percentage by weight based on the total weight of the alloy. The designation of the alloys is made in accordance with the regulations of The Aluminium Association, known to those skilled in the art. The definitions of the metallurgical conditions are given in the European standard EN 515. Unless otherwise stated, the definitions of the standard NF EN 12258-1 relating to aluminum and aluminum alloy products apply. Unless otherwise stated, the static mechanical characteristics, in other words the breaking strength R. m , the elastic limit in tension R p0,2and the elongation at break A%, are determined by a tensile test according to standard EN 10002-1 or NF EN ISO 6892-1. The compressive yield strength Rpc0.2 is determined according to standard ASTM E9-19, where the compressive yield strength Rpc0.2 corresponds to the stress corresponding to an offset of 0.2%. The location at which the parts are taken and their direction are defined by standard EN 485-1. The stress intensity factor (K Q ) is determined according to ASTM E 399-23. ASTM E 399 provides the criteria for determining whether K Q is a valid value of K 1C .For a given specimen geometry, the values ​​of K Qobtained for different materials are comparable to each other as long as the yield strengths of the materials are of the same order of magnitude. Unless otherwise stated, stress corrosion studies were carried out according to ASTM G47-22 (2022) and G49-85 (2023) in the Short Traverse (CT) direction. Stress corrosion tests are carried out under constant load using a device according to Figure 3 of ASTM G49-85 (2023). Here, the term "structural element" or "structural element" of a mechanical construction refers to a mechanical part for which the static and / or dynamic mechanical properties are particularly important for the performance of the structure and for which a structural calculation is usually prescribed or carried out. These are typically elements whose failure is likely to endanger the safety of the said construction, its users, its users or others.The products according to the invention are likely to be obtained by a process comprising the steps of casting, homogenization, hot rolling, solution treatment, quenching, controlled traction and tempering. The inventors have found that by adapting the composition of the product and controlling the hot rolling exit temperature, it is possible to improve the compromise Rp0.2(L)– K1c (LT), so as to obtain at mid-thickness a tensile yield strength Rp0.2(L) in the L direction of at least 435 MPa and a toughness K1c (LT) in the LT direction of at least 40 MPa.√m, while obtaining a compressive yield strength in the L direction of at least 435 MPa, good resistance to stress corrosion, as well as lower residual stress levels at mid-thickness. An aluminum alloy plate according to the invention is cast.The alloy according to the invention is an aluminum alloy of the 2xxx series comprising in weight percentage Cu: 4.5 - 4.9; Mg: 0.5 - 0.6; Mn: 0.2 - 0.4; Zn: 0 - 0.1; Ti 0.02 - 0.07; Ag: 0.1 - 0.4; Zr 0.08 - 0.15; Si: 0 - 0.1; Fe: 0 - 0.1; unavoidable impurities ≤0.05 each and ≤ 0.15 in total, remainder aluminum. The copper content of the alloy according to the invention is 4.5% to 4.9%. Preferably the copper content is at least 4.6%, or preferably 4.65% or 4.70% so as to obtain sufficient mechanical characteristics. Preferably, the maximum copper content is 4.85% or preferably 4.80% by weight so as to obtain sufficient toughness properties. In a preferred embodiment, the Cu content is 4.65% to 4.85% by weight. The magnesium content is 0.5 to 0.6% by weight.Preferably, the magnesium content is at least 0.50% by weight or 0.55% by weight so as to obtain sufficient mechanical characteristics, in particular the yield strength at mid-thickness. Preferably, the magnesium content is at most 0.60% by weight to obtain a sufficient level of toughness. In a preferred embodiment, the Mg content is from 0.50% to 0.60% by weight. The silver content is from 0.1 to 0.4% by weight, preferably from 0.10 to 0.40% by weight. Preferably, the silver content is at least 0.15%, or 0.20% or 0.25% or 0.30% so as to obtain sufficient mechanical characteristics. Preferably the silver content is at most 0.40% or 0.38% or 0.35% or 0.30% by weight. In a preferred embodiment of the invention, the silver content is 0.15 to 0.30% by weight. In another preferred embodiment of the invention, the silver content is 0.30 to 0.40% by weight.The manganese content is 0.2 to 0.4%, preferably 0.20 to 0.40%. Preferably, the manganese content is at least 0.25%, or even more preferably at least 0.30%. Preferably, the manganese content is at most 0.35%. In a preferred embodiment, the Mn content is 0.25% to 0.35% by weight. The zirconium content is 0.08% to 0.15%. Preferably, the zirconium content is at least 0.09% or 0.10% by weight. The inventors have found that the addition of Zr makes it possible to improve the Rp0.2(L) – K1C (L) compromise in combination with the hot rolling exit temperature. Preferably, the zirconium content is at most 0.14%, or 0.13% by weight. In a preferred embodiment, the Zr content is from 0.10% to 0.13% by weight and even more preferably from 0.10% to 0.12%. The zinc content is less than 0.1% by weight.Preferably, the zinc content is less than or equal to 0.05% by weight, or even 0.04% by weight. The alloy also contains from 0.02 to 0.07% by weight of Ti, preferably from 0.02 to 0.06% by weight and even more preferably from 0.02% to 0.05%, in particular to control the grain size during casting. A titanium content of less than or equal to 0.07% makes it easier to recycle the alloy according to the invention. A low titanium content of less than or equal to 0.07%, preferably less than or equal to 0.05%, makes it possible to increase the quantity of scrap (from the product according to the invention) used for the production of new products. Indeed, it is interesting to maintain a low titanium content in the scraps in order to allow the subsequent refining of new products, refining carried out using a refining agent containing Ti, such as TiB2 or TiC.It is preferable to limit the content of unavoidable impurities in the alloy so as to achieve the most favorable damage tolerance properties. The unavoidable impurities include iron and silicon, these elements have a content of less than or equal to 0.15% by weight each, preferably less than or equal to 0.12% by weight each, or even less than or equal to 0.10% by weight each. Preferably, the iron and silicon content is less than or equal to 0.08% or 0.07% or 0.06% or 0.05% by weight each. In a preferred embodiment according to the invention, the iron content is 0 to 0.12% or 0 to 0.10% or 0 to 0.08% or 0.03 to 0.12%, or 0.03 to 0.10% or 0.04 to 0.06%. In a preferred embodiment according to the invention, the silicon content is 0 to 0.12% or 0 to 0.10% or 0 to 0.08% or 0.03 to 0.12%, or 0.03 to 0.10% or 0.04 to 0.06%.The other elements considered as impurities have a content less than or equal to 0.05% by weight each and 0.15% by weight in total. The remainder corresponds to aluminum. The plate is cast by usual casting techniques such as for example semi-continuous casting. The plate has a substantially parallelepiped shape. The plate preferably has a thickness of 300 mm or more, for example 400 mm, 500 mm or 600 mm or any other intermediate values. After casting, the plate is generally scalped to eliminate the segregation zones near the surface while maintaining a substantially parallelepiped shape. The cast plate is then homogenized. The homogenization treatment is carried out at a temperature of 480°C to 540°C for 4 to 80 hours, preferably from 10 to 60 hours or from 20 to 50 hours. Preferably, the homogenization temperature is from 495°C to 540°C for 5 hours to 60 hours, preferably from 15 hours to 50 hours.The homogenization can be carried out in one or more stages, at least one of which is carried out at a temperature of 510°C to 540°C for 1 to 30 hours, preferably 5 to 25 hours. After homogenization, the plate is generally cooled to room temperature before being preheated to a temperature of 410°C to 480°C for hot rolling deformation. The preheating makes it possible to reach a hot rolling inlet temperature preferably of 380°C to 460°C and preferably of 400°C to 460°C and even more preferably of 420°C to 450°C, allowing the deformation of the plate. However, it is also possible to directly roll the homogenized plate without prior preheating if it is not cooled and has a sufficient temperature, preferably from 380°C to 460°C and more preferably from 400°C to 460°C and even more preferably from 420°C to 450°C, allowing the deformation of the plate.The hot deformation is carried out by hot rolling so as to obtain a sheet with a final thickness of at least 50 mm. Preferably, the final thickness is at least 75 mm or 90 mm. Preferably, the sheet has a final thickness less than or equal to 200 mm, preferably less than or equal to 180 mm or 160 mm or 130 mm. In a preferred embodiment of the invention, the final thickness is from 90 mm to 160 mm, or even from 90 mm to 130 mm. The hot rolling conditions are chosen such that the final hot deformation temperature is from 410°C to 445°C, preferably from 420°C to 440°C and even more preferably from 430°C to 440°C. To achieve this hot rolling exit temperature, the skilled person has various technical solutions at his disposal. Examples include the use of heating and / or cooling boxes to achieve an outlet temperature of at least 410°C.Heated rolling rolls or rolling scheme or waiting times between passes can also be used. The rolled sheet is then solution treated preferably by a heat treatment of 490 to 530°C for 15 min to 8 h, then quenched in water, typically water at room temperature, preferably below 40°C. The product then undergoes a controlled tensile strain of 3 to 6% and preferably at least 4.5%, typically about 5%. Tempering is then carried out at a temperature of 100 to 180°C for 5 to 100 h, preferably 120 to 170°C for 20 to 70 h.Preferably, the tempering is carried out in at least two stages according to the conditions of patent application WO2022 / 129806: - a first sequence whose temperature expressed in °C is described by a function ^1°^ (^) depending on the time t, such that the maximum temperature reached ^1^^^ is between 130°C and 180°C and the holding time t1 at a temperature between 130°C and 180°C is such that the equivalent duration. is between 10h and 80h, equivalent duration ^1 ^ ^ ^ ^ ^° calculated at a temperature of 160°C according to the formula - and a second sequence whose temperature expressed in °C is described by a function^2°^ (^) dependent on the time t whose temperature is such that ^2°^ (^) is less than ^1^^^and whose holding time t2 expressed in hours at a temperature between 100°C and 130°C is such that the equivalent time calculated at the temperature of 160°C according to the formula is between 0.3% and 15% of the equivalent duration ^1 ^ ^ ^ ^ ^°calculated for the first sequence. Preferably, the tempering is carried out in two stages, a first stage at a temperature of 140°C to 180°C for a duration of 10h to 100h, preferably 10h to 40h, and a second stage at a temperature of 100°C to 130°C for a duration of 10h to 50h, preferably 15h to 30h. In a preferred embodiment, the first stage is carried out at a temperature of 160°C + / -5°C for a duration of 18h + / -5h and the second stage at a temperature of 120°C + / -5°C for a duration of 20h + / -10h, preferably 20h + / -2h in order to improve the resistance to stress corrosion. Preferably, the tempering is such that the total equivalent time t tot eq at 160°C is from 10 to 90 hours. Preferably, the total equivalent time ttot eq at 160°C is at least 13h, preferably from 13 to 40 hours. It may be advantageous to aim for durations of total equivalent time ttot eq at 160°C of 13 to 25 hours in order to improve the resistance to stress corrosion.The total equivalent time ttot eq at 160°C is defined by the formula:. where the temperature expressed in °C is described by a function ^°^(^) dependent on time t. The function ^°^ (^) corresponds to the instantaneous tempering treatment temperature, which changes with time t (in hours). In the particular case of a plateau, the function ^°^(^) is constant during the duration of the plateau. ttot eq is expressed in hours. The constant Q / R = 16360 K is derived from the activation energy for Cu diffusion, Q = 136000 J / mol. The formula giving t_tot eq takes into account the heating and cooling phases. The preferred metallurgical tempers for sheets are T8, more particularly T84 or T86. The inventors found that by maintaining a hot rolling exit temperature of 410°C to 445°C, in combination with the selected composition, it was possible to improve the mid-thickness compromise Rp0.2 (L) – K1c (LT), while maintaining good quarter-thickness properties and good resistance to crack bifurcation.In fact, by maintaining a hot rolling exit temperature of 410°C to 445°C, in combination with the selected composition, it is possible to obtain a tensile yield strength of R at mid-thickness. p0.2 (L) and a compressive yield strength R pc0.2 (L) in the L direction, both of at least 435 MPa and a toughness K 1c(LT) in the LT direction of at least 40 MPa.√m, as well as good fatigue cracking behavior and good corrosion resistance. The inventors attribute this improvement to the mid-thickness granular microstructure, obtained on the solution-treated and tempered product, which comprises a surface fraction of recrystallized grains at mid-thickness of 50% to 80%, preferably 50% to 75%. The inventors have in fact noted that it is important for the structure to be predominantly recrystallized, i.e. to have a surface fraction of recrystallized grains of at least 50%, without however obtaining a completely recrystallized microstructure. It is indeed important to have a surface fraction of recrystallized grains of less than 80%, preferably less than 75%, and preferably less than 70%. The measurement of recrystallized surface fraction can be measured by EBSD. Preferably, the observation is made in the L-TC plane of the product.According to the invention, a grain is considered recrystallized if it has a misorientation of at least 7° with the neighboring grain and the orientations within said grain (also called GOS for Grain Orientation Spread) have an extent of less than 2.5°. The inventors have also found that by maintaining a hot rolling temperature at the outlet of 410°C to 445°C, in combination with the selected composition, a favorable texture is obtained at mid-thickness to optimize the compromise at mid-thickness Rp0.2 (L) – K1c (LT). This texture is such that the volume fraction of the Copper component {112} <111> is greater than 4%, preferably 5% and / or the volume fraction of Brass component {110} <112> is greater than 7%, preferably 8% and / or the volume fraction of component S{123} <634> is greater than 9%, preferably 11%.Preferably, the sum of the volume fractions at mid-thickness of the Copper {112} texture components <111> , Brass{110} <112> , and S {123} <634> is greater than 20%, preferably 25%, or even 30%. Texture quantification can be done from global measurements by X-ray diffraction or from local measurements by electron backscatter diffraction (EBSD) in a scanning electron microscope (SEM). The volume fractions of the different components present in the texture can then be accessed via the calculation of the crystal orientation distribution function (COD). The COD can be calculated by the spherical harmonics method from the measured pole figures (preferably at least 4 pole figures). The sample size is adapted to the grain size of the material.Preferably, if an RX measurement is used, the sample size is chosen so as to be able to analyze at least 3000 grains, preferably 5000. If the EBSD technique is used, the sample size is chosen so as to be able to analyze at least about a hundred grains, preferably at least 200 grains. It is possible to simplify the information contained in the FDOC. This is commonly done in the art in order to describe selected aspects of the distribution of orientations in the material. An example of this practice is the calculation of the volume fraction of crystallites that have a specific orientation. To do this, reference orientations are defined as well as an angle of maximum misorientation around these orientations. The FDOC is then integrated into the domain thus defined, which makes it possible to deduce the relative volume of orientations contained in this domain compared to the total volume.The present inventors used a tolerance of 15° around the orientations “copper”, “brass”, “S” in order to describe the texture obtained. The crystallographic orientations “copper”, “brass”, “S” are known to those skilled in the art and described for example in the reference document by UF Kocks, CN Tomé, and H.-R. Wenk, “Texture and anisotropy: preferred orientations in polycrystals and their effect on materials properties”. Cambridge University Press, 2000. The orientations “copper”, “brass”, “S” are reproduced in the table below. Name Indices Bunge (φ1,Φ, φ2) Kocks (Ψ,Θ,ϕ)Copper {112} <111^ > 90,35,45 0,35,45Brass {110} <1^12> 35,45,0 55,45,0S {123} <634^ > 59,37,63 149,37,27The inventors found that by maintaining an exit hot rolling temperature of 410°C to 445°C, in combination with the selected composition, the residual stresses in absolute values ​​were minimized at mid-thickness in the tempered state.The rolled product according to the invention, with a thickness greater than or equal to 50 mm, preferably between 90 mm and 160 mm, has at mid-thickness a tensile yield strength Rp0.2(L) and a compressive yield strength Rpc0.2(L) in the L direction, both of at least 435 MPa. The product has a toughness K1c (LT) in the LT direction of at least 40 MPa.√m. According to the invention, the term "tensile and compressive properties in the L direction of rolling at mid-thickness" means tensile or compressive tests carried out using test pieces taken from the sheet at a position centered on the mid-thickness of the sheet and which may include a portion of the thickness of the sheet between a quarter thickness and three-quarter thickness. Similarly, according to the invention, the term "toughness properties K" means. 1cin the LT direction at mid-thickness of the toughness tests carried out from CT specimens taken from the sheet at a position centered on the mid-thickness of the sheet and which can integrate a part of the thickness of the sheet between a quarter thickness and three-quarter thickness. The product according to the invention has a combination of strength and toughness properties which makes it particularly suitable for structural elements for the aerospace industry (aeronautics and space). For aeronautical applications, a representative structural element manufactured from the product according to the invention comprises a spar, preferably an integral spar, or any other similar parts machined from thick wrought sections. An integral spar is used when the spar is machined in one piece from a sheet according to the invention. The spar can be used in an aircraft wing box.The product according to the invention is also of interest for armor applications. The product according to the invention is particularly interesting as an armor plate used on armored vehicles, in particular on military vehicles such as tracked or wheeled combat vehicles, armored personnel carriers, armored support systems, amphibious assault systems, advanced assault amphibious vehicles or armed robotic vehicles. Preferably, the armor plate is one of the integral armor plates, i.e. machined in one piece from a plate according to the invention. Examples Example 1 Two compositions A and B (Table 1) were obtained by conventional semi-continuous casting. Composition B corresponds to the composition of the invention. The other composition A differs from the invention by the absence of zirconium. For each composition, two plates are available.[Table 1] – Chemical composition by weight %Si Fe Cu Mn Mg Zn Ti Ag ZrA Ref 0.04 0.08 4.63 0.31 0.56 0.006 0.03 0.37 0.00B Invention 0.04 0.08 4.71 0.30 0.57 0.003 0.03 0.36 0.11The trays thus cast were homogenized for 5 hours at 495°C + 18 hours at 525°C, scalped to a thickness of approximately 416 mm and then reheated before being hot rolled to reach a final thickness of approximately 101 mm. Taking into account the rise and fall times, the total homogenization time between 480°C and 540°C is approximately 42 hours. For each composition, we sought to test the mechanical properties obtained depending on whether the hot rolling exit temperature was 430°C to 440°C or less than 410°C. For this, the plates were reheated between 410°C and 480°C then hot rolled in such a way as to obtain the target temperatures.According to Table 2, the sheets for which an exit temperature above 430°C is targeted have a hot rolling inlet temperature above 410°C and the sheets for which an exit temperature below 410°C is targeted have a hot rolling inlet temperature below 410°C. This is one example among others to obtain the targeted hot rolling exit temperature. Indeed, there are other ways to reach the desired exit temperature; for example, the rolling scheme can be adapted by making, for example, larger reduction passes in order to reheat the metal. It is also possible to carry out intermediate reheating or, on the contrary, to carry out waiting times to ensure that the metal cools. The sheets thus hot rolled were then solution-treated for 5 hours at 524°C and then quenched in water at room temperature.They were then pulled so as to achieve a residual plastic deformation of approximately 5% to reach a final thickness of approximately 98.5 ± 5 mm. The sheets then underwent a two-stage tempering of X h 160°C + 20h 120°C with X = 18h, 36h and 54h. The total equivalent time at 160°C taking into account the rising and falling phases is respectively 20.4h, 38.5h and 56.4h. The sheets thus treated were then tested in order to measure the yield strength, the breaking load, the elongation as well as the toughness. The tensile specimens were taken at mid-thickness in the rolling direction L. The toughness specimens were also taken at mid-thickness and measured in the direction LT. The toughness specimens used are CT20W40 specimens (thickness B=20 mm, width W=40 mm according to the nomenclature of the ASTM E399 standard). [Table 2] Mechanical characteristics T. entrée T sortie Revenu X h Tequ 160°C + 20h total at Rp0.2 (L) Rm (L) A% (L) K1C(LT) LAC LAC 120°C 160°C t / 2 t / 2 t / 2 t / 2 °c °CX (h) hour MPa MPa % MPa.√m18 20.4 429 452 13.6 41.2A-1 Ref 389 385 36 38.5 426 450 13.2 40.654 56.4 427 453 12.2 39.918 20.4 428 452 14.3 43.9A-2 Ref 442 435 36 38.5 428 452 12.6 43.854 56.4 427 453 11.7 43.518 20.4 433 456 12.9 39.7B-1 Ref 393 392 36 38.5 430 454 13.4 38.954 56.4 428 453 12.1 37.918 20.4 442 466 13.4 45.0B-2 Inv. 444 434 36 38.5 442 466 12.7 43.854 56.4 440 466 11.4 43.2 It can be seen (see figure 1) that the B-2 sheets according to the invention present the best compromise Rp0.2 (L) – K1c (LT). The inventors found that the combined choice of chemical composition and hot rolling exit temperature between 410°C and 445°C not only increases toughness but also yield strength. Indeed, an increase in yield strength of approximately 10 MPa and toughness of approximately 5 MPa is observed.√m for a composition containing Zr if the hot rolling exit temperature is between 410°C and 445°C (Figure 1). For a composition not containing Zr, only an increase in toughness is observed. A texture measurement by X-ray diffraction was carried out on each of the sheets at mid-thickness. The present inventors used a tolerance of 15° for each of the orientations considered. The volume fraction in % of the brass, copper and S orientations, representative of the compression components, as well as the cube, Goss, CG 26.5 orientations representative of the components parallel to the direction <100> is given in Table 3.[Table 3] – volume fraction in % of texture orientationsSum Cube Goss CG26.5 Copper Brass S components {001} <100> {011} <100> {021} <100> {112} <111> {110} <112> {123} <634> Copper + Brass +S %% % % % % %A-1 5.8 3.3 7.3 2.8 5.9 7.8 16.5A-2 5.7 2.1 4.1 2.2 5.1 6.7 14.0B-1 4.8 2.5 6.2 2.8 5.8 7.7 16.2B-2 5.7 2.1 4.1 5.5 9.0 13.0 27.5The inventors have found that a product having a volume fraction of componentCopper {112} <111> greater than 4% is beneficial and / or a brass component {110} <112> greater than 7% and / or an S component {123} <634> greater than 9%. A sum of volume fractions of the copper texture components {112} <111> , brass {110} <112> and S {123} <634> greater than 20% improves the static-toughness compromise. The surface fraction of recrystallized grains was determined at mid-thickness for each of the tested sheets (Table 4). This measurement was made by EBSD measurement.The observations were made on a scanning microscope type FEG-SEM Ultra (Zeiss) under a voltage of 20 kV and a working distance of approximately 12 mm. The acquisition of the images is made using a Hikari EDAX camera with an acquisition step of approximately 0.75 µm. A grain is considered recrystallized if it presents a misorientation of at least 7° with the neighboring grain and the orientation of said grain has an extent of less than 2.5°, also called Grain Orientation Spread (GOS).[Table 4] Recrystallized fraction at mid-thickness determined by EBSDFrecrystallized surface fraction at t / 2% A. -1 91 A-2 95 B-1 92 B-2 62It is found that the B-2 sheet according to the invention has a recrystallized surface fraction at mid-thickness lower than the other sheets. The surface fraction of recrystallized grains is equal to 62%. The inventors attribute the better behavior of the B-2 sheet to a “predominantly recrystallized” mid-thickness granular structure, that is to say that the structure is not 100% recrystallized. We speak of a predominantly recrystallized structure according to the invention such that the surface fraction of recrystallized grains at mid-thickness is 50% to 80%. The residual stresses were evaluated on each of the sheets. The measurement of residual stresses is carried out according to the “bar method”. Two full-thickness bars are taken, in the L and TL directions, by sawing in each of the sheets. The sampling dimensions are: - for the bar in L direction: 450mm (L direction) x 35mm (TL direction) x thickness - for the bar in TL direction: 35mm (L direction) x 450mm (TL direction) x thickness.The bars are then machined to obtain a bar of length 440 mm, width 30 mm and thickness e (thickness of the sheet after tempering). The method includes the following steps: - Initial measurement of the deformation on the lower face of the bar: the bar is positioned on two supports approximately 435 mm apart so that a L-TL surface is in contact with the supports. Using a strain gauge glued to this face, at mid-length of the L-TL surface, the initial deformation is measured. - Machining of the bar in successive passes to remove 4 mm of its thickness until reaching a final thickness of approximately 6 mm. During each machining step, heating is limited to 5 ° C so as to avoid any influence of the machining conditions on the deflection measurements carried out. - Measurement of the deformation at the end of each machining pass using the strain gauge.From the deformation measurements made on each of the bars in the L and TL directions, it is possible to calculate the evolution of the residual stresses present in the sheet as a function of the position in the thickness of the sheet in the L direction. The calculation principle is well known. The principle is for example recalled on page 37 and following of Nicolas Chobaut's thesis "Measurements and modeling of residual stresses during quenching of thick heat treatable aluminum components in relation to their precipitation state" 2015 - Ecole Polytechnique Fédérale de Lausanne (https: / / doi.org / 10.5075 / epfl-thesis-6559). The evolution of the stress in the L direction according to the position in the thickness of the sheet is represented in Figure 2. It is observed that the B-2 sheet according to the invention has, at mid-thickness, the lowest residual stresses in absolute values. Stress corrosion tests were carried out on the products obtained according to the invention.The stress corrosion tests consisted of testing the B-2 sheets in the transverse direction after tempering for 36 hours at 160°C + 20 hours at 120°C (total equivalent time at 160°C: 38.5 hours) and 18 hours at 160°C + 20 hours at 120°C (total equivalent time at 160°C: 20.4 hours). The corrosion tests were carried out according to ASTM G44, with devices allowing the product to be tested under constant load according to ASTM G49-85 (2019) recommendations. The test consisted of determining, for different stresses between approximately 200 MPa and 330 MPa, the number of days of testing without a break appearing. It can be seen that tempering for 18 hours at 160°C + 20 hours at 120°C increases the stress corrosion resistance (Figure 3). Income X h 160°C + CSC stress (MPa)Number of days before 20h 120°C TC rupture 2. 01 27 238 19 6:02 p.m. 78 14 319 6 B-2 2 25 9 238 7 36h 2 79 5 321 4

Claims

CLAIMS1. A method of manufacturing wrought products made of 2xxx series aluminum alloy, comprising the following steps: (a) casting an aluminum alloy plate comprising, in % by weight, Cu 4.5 - 4.9 Mg 0.5 - 0.6 Mn 0.2 - 0.4 Zn 0 - 0.1 Ti 0.02 - 0.07 Ag 0.1 - 0.4 Zr 0.08 - 0.15 Si 0 - 0.15 Fe 0 - 0.15 Unavoidable impurities ≤0.05 each and ≤0.15 in total, remainder aluminum, (b) homogenizing said plate at a temperature of 480°C to 540°C for 4 to 80 hours, preferably 10 to 60 hours, (c) optionally, reheating said homogenized plate, (d) hot deforming by rolling said homogenized plate to obtain an intermediate product having a thickness greater than or equal to 50 mm, preferably from 90 mm to 160 mm, (e) said intermediate product is dissolved, (f) said dissolved intermediate product is quenched with water, (g) said dissolved and quenched intermediate product is pulled in a controlled manner with a permanent deformation of 3 to 6%,(h) said intermediate product thus dissolved, quenched and stretched is tempered by heating from 100 to 180°C for 5 to 100 hours, preferably the total equivalent time ttot eq at 160°C is 10 to 90 hours, preferably 13 to 40 hours, the total equivalent time ttot eq at 160°C is defined by the formula:, where ^°^(^) corresponds to the change in temperature expressed in °C as a function of time during tempering. characterized in that during step (d) the hot rolling outlet temperature is from 410°C to 445°C, preferably from 420°C to 440°C.

2. Manufacturing method according to claim 1 such that during step (h) the tempering is carried out in two stages, a first stage at a temperature of 140°C to 180°C for a duration of 10h to 100h, preferably from 10h to 40h and a second stage at a temperature of 100°C to 130°C for a duration of 10h to 50h, preferably from 15h to 30h.

3. Manufacturing method according to claim 2 such that the first stage is carried out at a temperature of 160°C + / - 5°C for a duration of 18h + / - 5h and the second stage at a temperature of 120°C + / - 5°C for a duration of 20h + / - 10h, preferably 20h + / - 2h.

4. Manufacturing method according to any one of claims 1 to 3 such that reheating is carried out during step (c) at a temperature of 410°C to 480°C.5.Manufacturing method according to any one of claims 1 to 4 such that in step (d) the hot rolling inlet temperature is from 380°C to 460°C.

6. Rolled product of 2xxx series aluminum alloy having a thickness of at least 50mm, preferably from 90mm to 160mm, comprising in % by weight,Cu 4.5 - 4.9Mg 0.5 - 0.6Mn 0.2 - 0.4Zn 0 - 0.1Ti 0.02 - 0.07Ag 0.1 - 0.4Zr 0.08 - 0.15Si 0 - 0.15Fe 0 - 0.15Unavoidable impurities ≤0.05 each and ≤0.15 in total, remainder aluminum, characterized in that, at mid-thickness, the grain structure of said product comprises a surface fraction of recrystallized grains of 50% to 80%, preferably of 50% to 75%, the surface fraction of recrystallized grains is measured by EBSD and where a grain is considered recrystallized if it has a misorientation of at least 7° with the neighboring grain and the orientation of said grain has an extent of less than 2.5°, also called Grain Orientation spread (GOS).

7. Rolled product according to claim 6 characterized in that the volume fraction of Copper component {112} <111> is greater than 4%, preferably 5% and / or the volume fraction of brass component {110} <112> is greater than 7%, preferably 8% and / or the volume fraction of component S {123} <634> is greater than 9%, preferably 11 %.

8. Rolled product according to claim 7 characterized in that the sum of the volume fractions at mid-thickness of the copper texture components {112} <111> , brass {110} <112> and S {123} <634> is greater than 20%.

9. Rolled product according to one of claims 6 to 8 characterized in that the Mgen content % by weight is 0.50 to 0.60.

10. Rolled product according to one of claims 6 to 9 characterized in that the Zn content in % by weight is less than 0.05.

11. Rolled product according to one of claims 6 to 10 characterized in that, at mid-thickness, the tensile strength in the L direction, Rp0.2 (L) measured according to standard EN 10002-1 and the compressive strength in the L direction, Rpc 0.2 (L) measured according to standard ASTM E9-19 is each at least 435 MPa.

12. Rolled product according to one of claims 6 to 11 characterized in that at mid-thickness the toughness K1c (LT) measured according to standard ASTM E399-23 is greater than or equal to 40MPa.√m.

Images